Apparatus for elevating concrete forms



March 23, 1954 R. l. PATTERSON ET AL 2,673,064

APPARATUS FOR ELEVATING CONCRETE FORMS Original Filed April l5. 1949 3 Sheets-Sheet l Mllflhl 23, 1954 R. l. PATTERsoN ET A1. 2,673Q64 APPARATUS FOR ELEVATING CONCRETE FORMS Original Filed April l5, 1949 5 Sheets-Sheet 2 W@ wiwfraz/vw;

March 23, 1954 R. l. PATTERSON ET AL APPARATUS FOR ET .EV'FING` CONCRETE FORMS 5 Sheets-Sheet 3 Original Filed April l5. 1949 rma/Yay: y

N 0 s: fr n 0 f Patented Mar. 23, 1954 2.67 3,064 APPARATUS FOR ELEVATIN G CONCRETE FORMS Roy I. Patterson and Herman W. Foss, Minneapolis, Minn., assignors to Minot Builders Supply Co., Inc., a corporation of Minnesota Continuation of application Serial No. 87,632,

April 15, 1949. This 1952, Serial No.

application November 320,228

9 Claims. (Cl. 254-106) Our invention relates to apparatus used in conjunction with the construction of concrete building walls. In general the invention relates to means for automatically elevating form sections used in constructing concrete Walls and in particular it relates to a jack or normally a plurality of jacks automatically actuated by fluid pressure means to progressively elevate form sections and a concrete pouring platform by small consecutive increments of distance as the wall is poured.

This application is a continuation of our application Serial No. 87,632, `filed April 15, 1949, now abandoned.

In pouring the concrete for large structures, such for example as concrete elevator bins or systems of concrete elevator bins, ithas been customary to provide form sections conforming to the wall to be built, and these forms are connected with a platform upon which the concrete is received and moved to be poured into the upper open end of the forms. An extremely difficult problem has been encountered, especially with large concrete structures, in raising one or a large number of relatively heavy form sections and the platform or flooring connected therewith, which may cover the entire area of the structure being built. The forms, usually around four feet deep, must be raised very slowly so that the concrete at the bottom of the form will have had time to sufliciently set before the supporting forms are drawn up and away from the formed concrete. Further, the forms should in general be raised at a substantially uniform speed about the entire circumference or extent of the walls and partitions being built.

One method of raising these forms which has been followed is to have vertical rods embedded in the concrete, and to clamp to these rods handoperated jacks which act to slowly lift the forms and the attached flooring; but this method involves a large number of workmen, is slow and uncertain in operation and frequently produces troubles which delay the pouring operation.

Another method disclosed in the prior art provides a mechanical jack wherein two sets of gripping dogs adapted to engage a jack rod are dis-` posed on opposite sides of the working surface of the lifting frame. This method has been unsatisfactory because the lifting frames which are frequently made of wood are subject to warping and distortion. Also it frequently occurs that all of the jacks do not provide the same degree of movement, which results in tilting of the flooring which in turn causes tilting of the lifting n frames to render thefjacks inoperative. This is particularly true when the sets of the gripping dogs are carried by members which are secured to the lifting frame.

We have discovered a more effective and more simple method of lifting the forms and the attached flooring than any yet disclosed in the prior art, whereby the jack surrounds a jack rod, but is independent of the lifting frame and therefore cannot be affected by warping or tilt-ing of the lifting frame. The present jack has an upper and a lower member encompassing the jack rod and forming an annular pneumatically expansible chamber. Both the upper and lower members are connected to rod engaging bits which are Supported by their respective members beneath the upper limits of the upper member and with their respective members form an integrated unit which lies entirely below the lower limits of the working surface of the lifting frame. Having our jack formed in such an integrated unit not only provides a cheaper and more simple device but due to the fact that it lies entirely below the working surface of the lifting frame it `may act on said lifting frame without being connected thereto and, therefore, will be independent of any tilting effect which has made prior automatic means for lifting concrete forms ineffective. y

We further discovered that a number of these pneumatic devices may be applied to concrete form sections throughout the circumference or total extent of the outer and partition walls, and that all of such devices may be caused to operate simultaneously by supplying high pressure compressed air to the expansible chamber of each of said devices, whereby the entire form structure and the attached flooring will be raised simultaneously by very small increments throughout the whole area of walls being built.

An object of our invention is to provide in combination with a lifting frame united with concrete form section and an adjacent flooring, and a jack rod embedded in the concrete between the opposite sides of the form, an improved lifting jack formed in an integrated unit and operative on the jack rod beneath the lower limits of the work surface of the lifting frame.

Another object is to provide a lifting jack which is independent of the lifting frame and is composed of a pair of movable members which encompass a jack rod beneath a working surface of the lifting frame, one of said members forming the lifting member and the other a follow up member to support the load on the rod during the movement of the lifting member, saidmembers being reslliently connected to each other,

chamber which is intermittently expanded tovr elevate a lifting frame, together with sets ofrod engaging bits connected to each of the members.

for engaging the jack rod beneath the upper limits of the upper member, anv adjustable resilient follow-up connection betweenv the members for adjusting the extent of liftingy action, said members and their respective sets of bits forming an integrated unit surface of the lifting frame 'on 'which'the iSack operates.

Other and further objects may be disclosedin.

the course of the following specification and claims, reference beinghadY to,A the accompany, ing drawings wherein:

'Fig'. `1 is a top pian 'View of a somewhat complicated series of walls such asmight result from building a small concrete country elevator, showing the distribution of lifting devices and the floor. and theupper edges of the concrete forms in'elation tothe numerouslifting devices emppyd Fig. 2 illustrates a side elevation part schematic sideview of, anV air tank, `a. valve for con.- i

trolling compressed air therefrom andmeans for automatically openingy and closing said valve.

Fig. 3 is a 'sideelevationpart sectionalviewof one ofjthe units taken on an'enlarged scale.

Fig'. '4 isa fragmentary side elevation sectional View offa modified form ofy pneumatic ber.

Fig. 5 is ar sectional .plan view taken on line 5.-'5.o`f.Fig. y'Shut on a reduced scale.

dis. a sectional plan view taken online G-SofFigf 3 but on a reduced scale.

Fig."7 isfa sectional planviewtaken on line 'I-"l of Fig. 3 with somepartsbroken away.

Fig. 8 is a side elevation View taken across one form section and-a part ofthe floor connected therewith of the frameworkfor carryingthelifting device with some parts insection.

A framework, shown in Fig. 8,for.each of Ythe lifting. devices employed, comprises .a lifting framedesignated generally4 by the numeral 9. This liftingframe has verticalsidemembers I0 and II, which may. be suitable studdingor vtimbers. To the members Il) and H. are secured by suitable means an upper set of cross pieces I2. andI3, see Fig. l, and corresponding sets ofY lower cross pieces designated at I4, it being un-V derstoodthat there is a second lower-crosspiece,

not'shown, parallel to upper cross piece I3, Fig.y

l. A working surface I 5, Figso and; is formed onthelower sideof the cross pieces `l2 and I3. As shown in Fig. l, there isa spacel I6 between the,.men1bers I2,

in Fig. 8. This jack rod'Il'is centered in both.

directions within the space 'I6' inthe lifting frame V3.

As shown on a small proportionate scale in Fig. 8, the vgeneral.referencefnumeral -2-I representsa pneumaticjack formed in/an integrated unit.. and 1 adapted to' act upon the working lsurbengafbfthe Working I3, I0 and Hof the liftingv frameS. Through this space extends a jaclerod' air chamn and the'lifting frame 9 is supported upon plate 26. This important feature of the present invention makestbejaclgZj effective against any tilting or stress .offthe'lifting frame 3. Plate 26 has a central depending boss 2l. A11 opening 28 in boss 21 is of ansize tov lit about the vertical rod 11; and` act as e.. guide to hold the plate 26 in proper alignin'en't with the rod I'l. The top plate 2B is secured to a lower plate 29 by means of a serieseof bolts 33, which are shown in elevation in Fig. 3 and in transverse section in Figs. 6 and 7.V The bolts 30 holdl the top plate 2,6 and the plate '.23 in fixed spaced relation by ,means of elongatedtubular spacer. members 3|which eX- tend. between thelowersurfaces of out-standing ears 32 on plate 26. and the upper surfaces. 0f similar ears 33 extending outwardly from plate 29. This arrangementpermits plate 29 to act asa guide tohold plate 26 in proper alignment with rod I1. The plate` 25,'Fig- .3, has formed integrally therewith or rigidly attached `thereto a depending annular flange '34 which forms a drum-likernember 35 which isopen at the Vbottom and which extendswithin the circle of bolts 3l! and spacers 3 I, as clearly shown in Fig.. 6.

The second member 23.. which `consists of. a plate 35, is held to the-,plate v2li` for movement in relation thereto by means of bolts -31 which exm tend through. ears `38 formed in the periphery of plate 36, see Fig. 6, and through similar ears `39 3, the bolts 3l. are extended some considerable distance on top plate 26. As clearly shown inFig.

above the upper surface o f plate 26 and each has on its topa nut 40 formed with a contactsun,

face or .attachedwasher 4l. Atubular spacer42 surrounds each boltY 3lvv between plate26 .and

distance above the upper. end of spacer 42, as,`

indicated at45inllig. 3. v'.lhisspace makes possible a relativev movement between the upper plateZ-Bandvthe lower vplate 3S while one or the other of said` members is heldin a stationary: position, andthe distance is made adjustable .byv

means of nuts 40.

The plate .36-is.circular )and is provided witha central circular opening llsfwhich fits sliflably about,y the outer surface 'of the tubular `boss '21,

as shown in Fig. 3. Theiouter 'circular edge '47' of plate 36 is-offsuch dimensionthatit lits slidably against the inner surface 'ofthe vdrum-'like member `35 to form an Yannular chamber 48. An annulardepend-ing` flange elle is Vformed on the undersideloflplate 3.6 and is'int'egrally connected Withan annular horizontal flange 59 which extends foutwardlyiintofthe fears 38'. There is thus formed-arightfangleabutment at'SI between the plate 3B-andthe-depending annular "flange 4S, as well as fan-.annular extension Ell'for supporting-thefears r38Ay so that the bolts. 37 'may come outside-ofthe outer -surface `Vof 'the yannular drum-like member-35, seerligxi;V

Withingthe -annular chamber llinside. of 1 drum 3Sangd;'outsde-of the' tubular boss 21de positioned .an enpansblie:annulanpneumatic :tube 4member 52. This tube will normally be flattened at its sides, but it has contact with the sides of top plate 26 and` bottom plate 36, as shown in Fig. 3. When compressed air, from a, suitable source hereinafter outlined, is admitted to the space within the pneumatic member 52 from air tube 53 through connecting nipple 54 and inlet opening 55, Fig. 3, it is clear that the force exerted by the compressed air will tend to separate top plate 26 and plate 36 to expand the chamber 48. If the plate 36 is anchored to the rod I1 while this force is exerted, plate 26 and all the parts connected with it which form the first member 22, will be raised a short distance determined by the extent of the space 45, which is adjustable by operation of nut 48. This adjustment may vary from one-quarter of an inch to one-half an inch, depending upon the concrete setting condition of the Weather at the time. It follows that when the rst member 22 is raised, which contacts directly the Working surface I of the lifting frame 9, see Fig. 8, the lifting frame 9 and all parts connected therewith, including the form sections and the floor, will be correspondingly lifted.

A variant form of pneumatic chamber is shown in Fig. 4. In place of the pneumatic tube 52, an annular rubber bottom liner 56 is set upon the upper surface of the plate 36. This is provided with an annular inner flap 51 which fits closely the outside of the depending tubular boss 21, and a similar `annular outer nap 58 about the outer circumference of the liner 56 fits closely the inner surface of drum 35. The pressure of the air admitted to chamber 68 in this form will cause the annular iiaps 51 and 58 to be pressed firmly against the respective outer surface of tubular boss 21 and the inner surface of the cylindrical drum 35 as the plate 26 and attached parts are moved upwardly. This willseal the chamber 48 against loss of air pressure and will permit the upper plate 26 to be lifted.

The sets of rod engaging bits indicated generally in Fig. 8 as 24 and 25 which support the members 22 and 23 for movement relative to each other will now be described in detail.

As shown in Fig. 3, secured to plate 36 are a number of bolt members 59 which are threaded at 68 into the plate 36. In the preferred arrangement of my invention there will be four of these members 59 each so connected with the plate 36 that they will be ninety degrees apart all the way around the jack rod |1. Each of these bolt members is identical with the others except as to position. The bolt members 59 in angular relation to the rod |1 and extend through an opening 6| in individual rod engaging bit 62. The bolt members 59 are threaded at 63 to receive thereon a nut 64. On the inner side of nut 64 is a coiled compression spring 65 which engages the center portion of bit 62. `Each of the rod engaging bits 62 has a semi-spherical end 66 which iits into the angle abutment 5| heretofore described. Opposite the semi-spherical end 66 of each of the bits 62 is a sharpened end 61 which is curved as indicated in Fig. `5. Nut 64 is adjustable so that the spring 65 may always hold the bit 62 in firm gripping engagement with the rod |1.

A similar arrangement of rod engaging bits are connected to plate 29 which forms a part of the rst member 22, as seen in Fig.` 8. Here each of the bolt members designated at 68 has a threaded end 69 which is threadedinto the plate 29.

Likewise, there are preferably fourof saidboltsfy are rigidly heldv Cil each carried angularly disposed toward therod |1, as shown in Fig. 3. Bolt members 68 extend through opening 69a in the rod engaging bits here designated at 10. The bolt members 68 are threaded at 1| to receive a nut 12 which compresses spring 13 against the rod engaging bits 18. Similarly the rod engaging bits 18 have rear curved ends 14, which engage angle abutments 15 between the lower side of plate 29 and depending ange members 16. Bits 10 have sharpened inner ends 11. The second set of four rod engaging bits and. their relation to rod |1 is shown in Fig. 5. This arrangement is shown for the lower set of rod engaging bits, as indicated by line 5 5, but it is identical with the arrangement of the upper set of rod engaging bits 62. As shown, the curved end 11 of bits 19 engages an are of the circumference of rod'l1.

Referring now to Figs. 1 and 8, the building construction used `in conjunction with the lifting frames 9, and the lifting jacks 2|, will be explained. Referring iirst to Fig. 8, the Wall forms are composed of a pair of members 18, 19 which as shown in Fig. 1, may be arcuate or of any particular configuration as is needed to form the walls of the desired building. Members 18, 19 are secured to the opposing legs I8 and of the lifting frame 9 by a plurality of supporting members designated at 98 and 8|. A oor surface is secured to one of the wall forms. Referring now to Fig. 1, is shown the manner in which the wall forms 18, 19 and the flooring 82 are arranged for the building of a grain elevator. The elevator construction here shown is composed of a rst bin 33, a second bin 84, with a plurality of smaller chambers designated at 85, 86, 81, 88, 89, 98 and 9|, being situated between the two large bins 83 and 84. It will be noted that a multiplicity of lifting frames 9 connect the Wall forms so as to simultaneously raise all portions of the Wall form as the building walls are constructed.

Referring now to Fig. 2, is shown the mechanism for energizing the lifting jacks 2|, consisting of an intermittently operable pneumatic system. On a platform 92, which in Fig. 1 is shown mounted in chamber 86, is a tank 93 adapted to contain air under pressure, supplied from a source not shown. An outlet conduit 94 carrying a gauge 95 and a control valve 96 permits air to pass through a conduit 91 to a mechanically operated timing valve 98 having an outlet conduit 99. A' valve plunger |00 which controls the passage of air through the valve 98 extends through the upper side of the timing valve 98 and is controllably moved by a beam lill supported on a bearing |82, and rotatably rocked by a motor driven cam |93, which rotates counterclockwise as shown by the arrow. The conduit 89, as seen in Fig. 8, extends to all of the multiplicity of jacks 2| and is with respect to each jack connected to the jack through the tube 53, shown in Fig. 3. A release valve |84 permits escape of air from the timing valve 98.

l The operation of the lifting jacks will now be explained. Assuming that a structure such as is designated in Fig. 1 has been started, and that air under pressure is present in tank 93, and that the cam |83 is periodically rocking the beam |9| to actuate the timing valve 98 to periodically permit air under pressure to pass through conduit 99 and through the individual conduits 53 to the chamber 48 of the jack shown in either Fig. 3 or Fig.. 4. When compressed air is introduced. intothepneumatic.member.41, of Fig.,

or into the chamber 48, of Fig. 4, above the diaphragm 54, it will apply opposing force between the top plate 2B and the bottom'plate 36, thereby tending to push these plates apart. Since plate 36 is held against movement in a downward direction by the multiplicity of bits S2, the upper plate 26 and all parts associated therewith will move upwardly raising the lifting frame 9, including the flooring on which the work is being performed. The extent of movement is limited by the space `45 between members 42 vand members 4l. During this movement the lower set of bits designated generally at 24 and consisting of bit members 10 will slidably move upwardly on the jack rod I1, while the upper set of bits and consisting of individual bits 52 will bite into the jack rod l1 and support the structure on the jack rod during the elevating movement. Assuming now that the forms and flooring have been raised to their maximum limit, cam |93 will have completed a circular movement, and air in the several chambers 48 of the multiplicity of jacks will then be released through the release valve |04 of the timing device 98, thereby diminishing the pressure within the chambers 48. When this occurs, the multiplicity of springs 44 which have been under compression, will expand to move the lower plates upwardly. This second action causes the Weight of the structure to be borne by the lower set of bits 24, since the upper set of bits 25 will move simultaneously with the plate 36. During the process of periodically raising the forms, the multiplicity of jacks, even though connected to a common source of pressure in tank 93, may not all move the same distance, and this will likely cause a tilting of the licor 82 and some of the forms 9 with respect to their wall structure. Individual adjustment of jacks may take place through valve means not shown, but connected between conduit 99 and each of the individual conduits 53 to the respective jacks. However, any tilting of the lifting form will have no effect on the operation of a particular jack, since each jack is situated beneath the working surface I5 of its respective frame, and therefore will not be influenced by the tilting of the frame. It should be understood that any tilting of any frame would only be a relatively small amount, but this has been a diflicult problem to overcome and has been the source of a great deal of difficulty in using these automatic jacks.

The advantages of our invention reside in the use of automatic jacks, which may be coupled into a parallel pneumatic system to automatically raise a building form during the construction of the walls thereof.

A particular advantage resides in providing jacks which are independent of the lifting frames and are formed as integrated units to be situated beneath the working surface of lifting frames to automatically raise the frames at a predetermined rate as the concrete is poured between the frames.

As numerous changes might be apparent to those skilled in the art, our invention is not conned to the specific structure shown, but is defined in the terms of the appended claims.

We claim:

l. A jack for supporting and raising a lifting frame on a jack rod, comprising a first movable member encompassing the jack rod and formed to act on a lower portion of a work surface of the frame, a second movable member encompassing the jackrodbeneath therst member, said second `member being spaced beneath the rst member, means acting within the space between said members for intermittently moving said first member vertically on the jack rod and relative to the second member to raise the lifting frame, means connecting said members and forming a resilient follow up connection for moving the second member vertically on the jack rod in the direction of the first member between intermittent movements of the first member, a first set of rodL engaging bits connected to said first member and having sliding engagement with the rod when said first member is moved, and a second set of rod engaging bits connected to the second member, both of said sets of bits supported by their respective members beneath the upper limits of the first member and with their respective members forming an integrated unit beneath the lower limits of the work surface of the lifting frame.

2. A jack for supporting and raising a lifting frame on a jack rod, comprising a first movable member encompassing the jack rod and formed to act on a lower portion of a work surface of the frame, a second movable member encompassing the jack rod beneath the first memberl an intermittently operable driven member positioned between said lirst and second members and acting on the rst member to move said first member vertically on the jack rod relative to the second member, means connecting said members and forming a resilient follow up connection for moving the second member vertically on the jack rod in the direction of the first member between intermittent movements of the first member, a first set of rod engaging bits connected to said first member and having sliding engagement with the rod when said first member is moved, and a second set of rod engaging bits connected to the second member, both of said sets of bits supported by their respective members beneath the upper limits of the rst member and with their respective members forming an integrated unit beneath the lower limits of the work surface of the lifting frame.

3. A jack for supporting and raising a lifting frame on a jack rod, comprising a rst movable member encompassing the jack rod and formed to act on a lower portion of a work surface of the frame, a second movable member encompassing the jack rod beneath the first member, a pressure operated device positioned between said members, intermittenly operable pressurizing means connected to said pressure operated device and effective to raise the first movable member on the jack rod relative to the second movable member, means connecting said members and forming a resilient follow up connection for moving the second member vertically on the jack rod in the direction of the first member between intermittent movements of the first member, a first set of rod engaging bits connected to said first member and having sliding engagement with the rod when said iirst member is moved, and a second set of rod engaging bits connected to the second member, both `of said sets of bits supported by their respective members beneath the upper limits of the first member and with their respective members forming an integrated unit beneath the lower limits of the work surface of the lifting frame.

4. A jack for supporting and raising a lifting frame on a jack rod, comprising a first movable member encompassing the jack rod and formed to act on the lower portion of a work surface of the llifting frame, -a second movable member er1- compassing the jack rod beneath the first member, means acting between said members for intermittently moving the' first member vertically on the jack rod and relative to the second member, ing a resilient follow up connection for moving the secondmember vertically on the jack rod in the direction of the first member, guiding means rigidly united with the iirst member and embracing the jack rod beneath the second member for holding the first and second members in vertical alignment with the jack rod, a rst set of rod engaging bits connected to said first member beneath its upper limits and having sliding engagement with the jack rod when said first member is moved, and a second set of rod engaging bits connected to the second member, both of said sets of bits supported by their respective members beneath the upper limits of the rst member and with their respective members forming an integrated unit beneath the work surface of the lifting frame.

5. A jack for supporting and raising a lifting frame on a jack rod, comprising a first movable member encompassing the jack rod and formed to act on a lower portion of a work surface of the frame, said member having a depending peripheral flange forming a chamber on the lower surface of said member, a second movable member encompassing the jack rod and positioned within the peripheral flange of the first member to form a lower surface of said chamber, means for intermittently introducing a pressure duid into said chamber for moving said rst member relative to the other member, a plurality of guide rods extending between the peripheral limits of said rst and second members, a spring surrounding each of said rods and engaging one of said members and with the respective guide rod forming a follow up connection between said members for moving the second member in the direction of the first member between intermittent movements of the first member, a first set of rod engaging bits depending angularly from said first member and engaging the jack rod, and a second set of rod engaging bits depending angularly from the second member and engaging the jack rod, both of said sets of bits supported by their respective members beneath the upper limits of the rst member and with their respective members forming an integrated unit beneath the lower limits of the work surface of the lifting,r frame.

6. A jack for supporting and raising a lifting frame on a jack rod, comprising a first movable member encompassing the jack rod and formed to act on a lower portion of a work surface of the frame, said member having a depending peripheral ange forming a chamber on the lower surface of said member, a second movable member encompassing the jack rod and positioned within the peripheral flange of the rst member to form a lower surface of said chamber, means for intermittently introducing a pressure fluid into said chamber for moving said first member relative to the second member, a plurality of guide rods extending between the peripheral limits of said rst and second members, a spring surrounding each of said rods and engaging one of said members and with the respective guide rod forming a follow up connection between said members for moving the second member in the direction of the first member between intermittent movements of the first member, limiting means cooperable with each of said means connecting said members and formspring meansfor limiting the extent of move-` ment of the first member relative to the second member, a first set of rod engaging bits connected to said first member beneath its upper limitsand having sliding engagement with the rod when the first member is moved, and a second set of rod engaging bits connected to the second member, both of said sets of bits supported by their respective `members beneath the upper limits of the rst member and with their respective members forming an integrated unit beneath the work surface of the lifting frame.

7. A jack for supporting and raising a lifting `frame on a jack rod, comprising a rst movable plate encompassing the jack rod and formed to act on a lower portion of a lifting frame, said plate having a depending peripheral flange forming a chamber on the lower surface of said plate, a second movable plate encompassing the jack rod beneath the first plate and positioned within the peripheral ange of the first plate to form a lower surface of said chamber, air sealing means within the chamber and independent of each of said plates, bolts extending between the outer portions of each of said plates, a coil spring surrounding each of said bolts and normally moving said plates to maximum separated position, an annular abutment formed on the bottom plate, a plurality of bolts secured to the bottom plate and extending angularly therefrom, a plurality of clamping bits each having an opening through which the bits are loosely held by said bolts, said bits being otherwise unconnected with any member with a sharpened end edge engageable with the jack rod and with its other end engageable with saidabutment, and a spring surrounding the bolt and forcing the sharpened edge of the bit against the jack rod.

8. A jack for supporting and raising a lifting frame on a jack rod, comprising a first movable plate encompassing the jack rod and formed to act on a lower portion of a lifting frame, said plate having a depending peripheral flange forming a chamber on the lower surface of said plate, a second movable plate encompassing the jack rod beneath the rst plate and positioned within the peripheral ange of the first plate to form a lower surface of said chamber, the top plate formed with a boss surrounding the jack rod, air sealing means independent of the plates within said chamber, a plurality of bolts extending through the outer portions of said plates, coil springs surrounding said bolts and normally holding the plates in maximum separated position, a third plate surrounding the jack rod below the second plate and connected to the top plate, an abutment formed on the lower surface of the bottom chamber plate and the third plate, sets of bolts secured to the bottom chamber plate and the third plate, sets of clamping bits each having an opening through which the bits are held by said bolts, said bits being otherwise unconnected with any member, but having sharp end edges engageable with the jack rod and having their other ends engaging the respective abutments, and a coil spring surrounding each bolt and engaging the respective bit for holding the sharpened end of the bit against the jack rod.

9. A jack for supporting and raising a lifting frame on a jack rod, comprising a first movable plate encompassing the jack rod and formed to act on a lower portion of a lifting frame, said plate having a depending peripheral `flange forming a chamber on the lower surface of' said I surrounding said bolts plate, a second movable plate encompassing the jack rod beneath the rst plate and positioned within the peripheral flange of the rst plate to form a lower surface of said chamber, one of said plates formed with a boss surrounding the jack rod, air sealing means independent of the plates within the chamber, bolts extending through outer portions of both plates, coil springs and normally moving the plates a maximum separated position, a third plate below and spaced from the bottom plate and connected with the top plate, abutments formed on the undersides of the bottom plate and the third plate, sets of clamping bits eX- tending angularly between said abutments and the jack rod, said bits having sharp end edges 12 the rod and having their other ends engaging the respective abutments, and springs engageable with the bits for forcing the sharp end edges of the bits against the jack rod.

ROY I. PATTERSON. HERMAN W. FOSS.

engageable with References Cited in the le of this patent UNITED STATES PATENTS Laffaille Feb. 6. 1951 

